IT201800004550A1 - FABRIC IN PLASTIC MATERIAL FOR THE SHADING OF GREENHOUSES AND OPEN FIELD CROPS - Google Patents

Description

FABRIC IN PLASTIC MATERIAL FOR THE SHADING OF GREENHOUSES AND OPEN FIELD CROPS

The present industrial invention relates to a plastic material fabric for shading greenhouses and open field crops, whose composition and textile pattern are optimized in order to obtain diffused light in the shaded environment.

The maximization of diffused light will also allow its use for different applications, such as the covering of tensile structures for sports or recreational use.

Preliminarily, it is specified that the term "net", where used, is to be understood in the present context as synonymous with the term "fabric", that is, a flat, thin and flexible product made by intertwining threads according to a specific pattern.

State of the art

It is known that in greenhouse crops the increase in diffused light that reaches the plants is advantageous for crop yields, since it reduces plant burns caused by direct light and increases the amount of light that reaches the lower leaves. Some studies also show that increasing the amount of scattered light would reduce the proliferation of fungi and insects.

For this reason, some roofing solutions for greenhouses that attempt to optimize this aspect are known to the state of the art. An example is described in the Italian patent IT1095475 which describes a polymeric composition for the production of films for use in agriculture to which, to improve the light diffusion properties, a mixture of basic metal sulphate is added. Chinese patent application CN104072844 describes the composition of an LDPE film for use in agriculture to which zinc oxide or magnesium oxide are added to improve the light diffusion properties. Mexican application MX2008005546 describes plastic films for covering greenhouses in which an additive to absorb ultraviolet is added to a base of LDPE, LLDPE and EVA. The Japanese application JP2014195424 describes the use of mica particles as an additive to improve the diffusion of light through the covering film.

Almost all the documents known to the state of the art that deal with improving the light transmission properties concern changes to the composition of the plastic used to make covering films (thin films), not shading nets. In fact, according to what is known in the state of the art, the nets for shading applications are optimized only with reference to their textile scheme to optimize the degree of shading, as described for example in the document DE3035232, in which a textile scheme including threads is described. of elastic warps by means of which the degree of shading can be varied by acting on the tension of the fabric.

All the ways of making greenhouse covers known to the state of the art are limited from a technical point of view. In fact, the use of covering film instead of nets prevents natural ventilation of the greenhouse, as opposed to what does not happen with the use of nets. On the other hand, the ways of making shading nets known in the state of the art are limited, as they are not optimized to maximize the mechanical strength of the nets and, at the same time, to increase the amount of diffused light.

Purpose of the invention

The purpose of the invention object of the present invention is to provide a net for shading greenhouses or open field crops whose textile pattern and material are optimized to maximize the amount of light diffused inside the greenhouse.

According to another purpose, the invention object of the present invention intends to provide a network in which the optimization of the amount of diffused light takes place without appreciable changes in the resistance of the network.

Still a further object of the invention object of the present invention is to provide a net for shading greenhouses in which the textile scheme includes the use of a strip and the material of which is preferably HDPE with the addition of an additive capable of absorbing infrared radiation. and enhance the light scattering effect.

Brief description of the invention

The invention achieves the purposes since it is a shading net in plastic material for covering greenhouses, made by means of a weaving scheme comprising at least one weft and a warp characterized in that at least for the realization of the weft, said weaving scheme is a strip of plastic material is used and by the fact that the composition of said plastic material includes PE (Polyethylene) to which at least one additive capable of absorbing infrared rays and increasing the light diffusion effect is added.

Detailed description of the invention

As shown in the attached figures, and as will be clear from the following description, the net object of the present invention has a textile pattern characterized by the use of a strip, at least for the weft and preferably for both the weft and the warp.

The characteristics of the network according to the invention were tested by means of spectroradiometric measurements and by means of field tests, by installing the network on some greenhouses and on open field crops.

It has been generally observed that the nets according to the invention allow greater productivity (for example in the cultivation of salads and spinach) than other nets known in the state of the art and commercially available; It has also been observed that, for this purpose, the presence, in the textile scheme, of the HDPE strip is important, which, with the same resistant section, has a significantly lower thickness than the circular section yarn. In fact, in confirmation of this interpretation, field tests have shown that by increasing the thickness of the strip used, the light diffusion effect decreases.

The net according to the invention can be made with weft in band and warp in circular section yarn or, preferably, with weft and warp made in band. Even more preferably, the net according to the invention will be made with weft and warp in band and knotted weaving, in order to minimize the actual thickness of the net with the same thickness of the band.

In addition to the use of the strip in the textile scheme, another characteristic of the net according to the invention is the use of strips and yarns in PE (Polyethylene) to which it is added, in the spinning phase (for the yarns) or in the spinning phase (for the strips), at least one additive capable of absorbing infrared rays and increasing the light diffusion effect.

According to a preferential embodiment, the additive is a mineral additive chosen from among Carbonates (Calcite, Dolomite, Anchorite, Magnesite, Rhodochrosite), sulphates (Alunite, Jarosite, Gypsum), Phyllosilicates (Clays, Chlorites), hydroxylated silicates (Epidote, Amphibole) used in percentages - with respect to the composition - lower than 10%. The examples in brackets for each group are intended as examples and not exhaustive, as any additive that has the characteristics of absorbing infrared radiation and increasing the diffusion effect of light can be used for the realization of the invention.

According to a preferential embodiment, the additive used includes calcite and is present, in the composition of the yarn and the band in percentages by weight of less than 10% and preferably between 4 and 6%.

Furthermore, according to a preferential way of construction, the net according to the invention will be made of white PE

The foregoing is confirmed by a series of spectrophotometric measurements made by today's inventors, the results of which are shown below.

The following tables show the results deriving from the application of an additive capable of absorbing infrared rays, in a percentage of about 5%, to Milk White (BL) or Transparent White (BT) polyethylene nets, made in band for both the weft and the warp. Table 1 shows the characteristics of the various types of networks tested, table 2, for each of these networks, shows the quantity of light (in percentage) that passes through them, as total transmission, as diffuse transmission and as Haze (ratio between both). This information is provided per frequency band (visible = 380-760 nm, Infrared 760-2500 nm, Ultraviolet 280-380 nm).

These are three types of networks that have been measured both with the addition of an additive (suffix -2 in the network code) and in the absence of the same (suffix -1 in the network code). The textile schemes of the three nets are shown in the photographs shown in figures 1 to 3 attached.

Table 1

As can be seen from the results in table 2, the application of an additive increases the percentage of diffused light (Haze) in all cases. This increase is particularly relevant for the 2641 network in all the frequency bands considered, but particularly in the infrared, where the Haze triples. It should be borne in mind that the nets 2641 and 2694 have the same weaving pattern, while the netting 6040 has a different weaving pattern. The difference between 2641 and 2694 is in the thickness of the strips used, which are considerably thinner in the 2641. The result is a more relaxed texture, in which the strips are stretched and can be crossed by the light in the direction of their thickness.

It is specified that the thicknesses indicated in the table are those of the strip before the weaving operation. As is well known, during the weaving operation the strip is stretched, and therefore its thickness decreases significantly.

The thicknesses measured after the weaving operation, for the nets preferably used to make the invention, are between 15 and 70 microns.

Table 2

Therefore, with a much lighter net (40 g / m <2> against 95 g / m <2>) a percentage of diffused light (about 22% in the visible) is obtained much higher than that which would be obtained in the absence of additive (about 7% in the visible).

The thermal effect of the application of the additive can be verified from the following table, which shows the direct infrared transmission value. The additive reduces this value by approximately 32% for the 6040 network, by approximately 15% for the 2641 network and by approximately 3% for the 2694 network.

Table 3

In general, and particularly in the case of the network in strip with a thickness of 79 / 50um (network 2641), the application of the additive allows to increase the total transmission of the network (thus increasing the amount of energy that can enter with solar radiation) and to decrease direct infrared transmission (thus reducing thermal losses), with an evident increase in temperature inside a greenhouse covered by the network.

From the evaluation of the haze (defined as the ratio between the diffused transmitted light and the total transmitted light) it can be deduced that in the 2694-1 only 61% of the total transmitted light is transformed into diffuse, while in the 2694-1 (with additive) the 74% is transformed into widespread. From these results it can be concluded that the additive increases the spread by 12%.

The porosity observed under the microscope is shown in the last column on the right of table 3. The fact that the amount of direct transmitted light decreases with the addition of the additive and approaches the value of porosity (which obviously, being the same , does not change with the addition of the additive) means that the addition of the additive significantly increases the diffusion of the light passing through the strips and, ultimately, significantly limits the direct transmission through the strips.

It has also been observed that the application of the same additive on wire nets, with flat weaving, does not have the same effects, as can be seen from the data in tables 3 and 4, in which it is seen that the scattered light values even decrease. if the additive is used in nets woven with circular cross-section yarn, such as 3350 netting, the textile scheme of which is shown in figure 4.

Table 4

Table 5

In monofilament nets, the additive does not make any improvement contribution to the diffusion of light, as the monofilament has a thickness and a geometric shape such as to make it similar to an opaque body. The result is that the light does not pass through the monofilament, but only passes through the holes in the mesh.

In strip nets, on the other hand, the additive is effective in improving the diffused transmission of light, since direct light passes not only through holes in the mesh but also through the thickness of the strip, therefore in the presence of additive, the diffusion increases significantly. important compared to a strip without additive.

A further aspect (in addition to the use of a strip instead of the circular section wire and the thickness of the strip) that significantly affects the performance of the nets is given by the density of the textile pattern. Spectrophotometric tests have shown that a mesh (2571 in figure 5) with a textile pattern similar to that of 2694, but with a thicker band (260 and 60 um respectively for the warp and for the weft) and with a more dense (6 warps / cm) does not benefit, in terms of diffused light, from the inclusion of the additive in the composition.

In fact, from the point of view of the textile scheme both fabrics in the warp make the jump of a needle [0-1 / 1-0 // x6 E6] while in the weft they make a jump of 5 needles [0-0 / 5-5 // x6 E6]. The 2694 has 3 warps / cm while the 2571 has 6 warps / cm, this implies that in the 2694 the knot is wider and the straps are positioned side by side while in the 2571 the knot is narrower and the straps overlap perfectly on top of each other (see fig. 5).

The fact that in 2571 the strips overlap implies that the overall thickness of the film affected by the diffusion increases with consequences of less influence of the additive, which does not happen for the 2694 where the strips are side by side and the thickness affected by the diffusion remains unchanged.

Preferably, therefore, the net according to the invention will be made with a textile pattern having up to 5 warps / cm, and even more preferably between 2 and 4 warps / cm.

It is therefore evident that, to maximize the thermal effect, the use of a particular textile scheme or the use of an additive in the composition of the net is not sufficient, but it is necessary that both factors are present, and that they are preferably linked to the use of thin strips, in order to optimize the thermal effect (intended as an effect on the temperature variation induced below the mesh with respect to the weight (and, therefore, the cost) of the mesh used.

Another factor that has a synergistic effect with those just described is the color of the yarn. The observations shown refer to milky white (i.e. opaque white) and transparent white nets, for which the addition of the additive has, as shown, an influence on the amount of diffused light that passes through the strip.

Similar tests were carried out with other colored nets, and in particular with gray nets, observing that the same results are not obtained.

Claims (6)

CLAIMS 1. Plastic fabric for covering greenhouses or for the protection of open field crops or the construction of tunnels, made using a weaving scheme comprising at least one weft and one warp characterized by the fact that at least for the realization of the weft of said weaving scheme a strip of plastic material is used and by the fact that the composition of said plastic material includes PE (Polyethylene) to which at least one additive capable of absorbing infrared rays and increasing the light diffusion effect is added. 2. Plastic material fabric for covering greenhouses or for the protection of open field crops or construction of tunnels according to claim 1 characterized by the fact that said at least one additive comprises a mineral additive selected from carbonates, sulphates, phyllosilicates , hydroxylated silicates, used in percentages lower than 10%. 3. Shading fabric in plastic material for covering greenhouses or for protecting open-field crops according to claim 1 or 2, characterized in that said at least one additive comprises calcite. 4. Shading fabric in plastic material for the covering of greenhouses or for the protection of crops in the open field or for the construction of tunnels according to one of the preceding claims characterized in that a strip is also used for the realization of the warp of said weaving scheme in plastic material. 5. Shading fabric in plastic material for covering greenhouses or for protecting crops in the open field or for building tunnels according to one of the preceding claims, characterized in that it is made of opaque white or transparent white Polyethylene. 6. Shading fabric in plastic material for the covering of greenhouses or for the protection of crops in the open field or for the construction of tunnels according to one of the preceding claims characterized by the fact that the thickness of said strips is between 15 and 70 microns and by the fact that the weaving is made with a textile pattern having up to 5 warps / cm, and even more preferably between 2 and 4 warps / cm.